🎮 Games › 🎬 Lesson videos › Picture Book: The Dented Ping-Pong BallPicture Book: The Dented Ping-Pong Ball
⏱ 0:48 📘 Grade 4 Science · Term 1 · Lessons 7–9
Little Bear’s dented ping-pong ball pops back out in hot water: the air inside expands. Water expands too — that’s how thermometers work. Rails have gaps, sky lanterns rise, and ice is the exception.
The videos are narrated in Mandarin Chinese with on-screen subtitles.
📚 What you will learn
Air expands when heated: a dented (unbroken) ping-pong ball pops out in hot water. Water expands when hot and shrinks when cold; thermometers use this. Solids expand too: rails need gaps, power lines sag in summer. Hot air rises (sky lanterns); water expands when it freezes — an exception.
🎙️ What the video says (in Chinese)
绘本故事《瘪了的乒乓球》。熊妹妹不小心把乒乓球踩瘪了。熊妹妹：呜呜，我的乒乓球！ 熊哥哥：别哭，把它放进热水里试试！过了一会儿，乒乓球慢慢地鼓起来了！ 熊妹妹：这是为什么呀？熊哥哥：球里的空气受热膨胀，就把瘪下去的地方撑起来了。这叫热胀冷缩。 熊哥哥：水也会热胀冷缩：放进热水，细管里的水往上升；放进冷水，水又降下来。熊妹妹：温度计就是这样测温度的！ 铁轨之间留着缝隙，因为夏天钢轨受热会变长。热空气往上升，孔明灯就飞起来了。 熊妹妹：原来，物体大都会热胀冷缩！不过，水结冰的时候，体积反而会变大，这是一个特例。
✏️ Try it yourself
Why does a dented ping-pong ball pop out in hot water?
Show answer The air inside expands when heated
Why do rails have gaps?
Show answer They get longer in summer heat
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